In many simple thin film fabrication processes, convenient diode fabrication processes may be difficult and/or expensive to implement. As a consequence, in many thin film processes, diode-connected transistors are used to simulate diodes in circuits. Diode-connected transistors may suffer from a potential drawback in thin film transistor (TFT) processes, in that the threshold voltage of TFTs in many TFT processes may shift from run to run, or from lot to lot. As a result, diode-connected TFTs made by such processes may show some variation in forward voltage drop, and the variation at times can be unacceptably large. This is particularly unfavorable when the diodes or diode-connected TFTs are used in reference voltage supply circuits. As a consequence, there is a need for a diode connected TFT architecture that is more tolerant of process-induced threshold voltage variations.